Wind energy plants work on the principle of aerodynamic force. The wind striking the rotor blade creates positive pressure below the sail, whilst there is negative pressure above the sail. This pressure differential generates a lifting force which modern wind energy plants utilise for movement and thus for electricity production.
Force 3 winds, which are common over the North Sea, the southern tip of South America, the Australian island of Tasmania and the Great Lakes in the north of the USA and other areas, are especially advantageous for wind energy plants. It merely remains to harness this wind. Measurements made by US-American researchers in 8,000 locations have shown that we could meet the world’s electrical energy requirements with wind power – on the condition that we use it more effectively.
In February 2005, the largest wind energy plant in the world began operation in Brunsbüttel in Germany. The 183 metre high giant "REpower 5M" has a rotor diameter of 126 metres which sweeps across an area of two football fields per revolution. The plant can provide up to five megawatts of electricity which is enough to supply around 4,500 households – an achievement which is unmatched worldwide.
Suitable areas for large wind power stations are, however, scarce – therefore great hopes are being placed in wind power plants at sea. Worldwide, some offshore wind parks have now been set up, for example in Denmark, Sweden, the Netherlands, Germany and England. The fact that the energy yield at sea is around 50 percent higher is due, amongst other factors, to the fact that water surfaces offer almost no friction to the wind. From a technical point of view, however, the offshore plants are considerably more costly than wind power stations on land because they have to brave high waves, storms and ice. This makes them around 60 percent more expensive than comparable onshore wind parks. In addition, the offshore power stations produce low frequency sounds which could drive away birds, fish and marine mammals.
The idea of a flying wind park sounds like something from science fiction. It would have two rotors and produce electricity at a height of five kilometres where strong, regular winds blow. The flying power station would be held by a cable which would also transport the electricity gained to the ground. It would take to the skies in a way similar to a kite and remain stable once in the air. However, it is still wholly uncertain whether this kind of airborne wind park will ever be built.